Until now to realize a process of the type described it was necessary to perform a number of operations, partially automatic, in which lenses were reloaded or substrates mounted on many and different machines, and then cleaning processes, were effected, resins were applied, drying was carried out, and so on.
All these operations required, additionally, the use of aspirant hoods. In fact the operator was exposed to solvents and resin vapors which are noxious, as known.
Recently there has been a trend to make optical components from plastic materials, for example CR39, known to the worker skilled in the art, ophthalmic articles. In addition optical components of plastic material have spread throughout commercial and scientific sectors.
However optical components in plastic material have hitherto involved not negligible drawbacks including:
Insufficient surface hardness, which makes the substrate surface vulnerable to abrasion with subsequent interference with transparency.
Sensitivity to heat which strongly decreases the ability to use the process for optical and thin film coatings.
An expansion coefficient which is greater than that of inorganic materials usually employed to effect optical and thin film coating.
Currently, some of these drawbacks are partially resolved by lacquer and immersion processes, for hardening the substrate surface, and by making thin film deposition almost cold by integrating traditional thermic evaporation with ionic bombardment.
These processes, however, often produced coatings which rapidly deteriorated, and/or with adverse environmental effects.
Hardening processes which are more innovative can be found in the market, based on the PECVD technique, for instance the process utilized at Balzers (Lichtenstein) and in antireflex coating of the plasma assisted type.
For example in processes realized by Laybold, and OCLI (U.S.A), the technique of magnetron sputtering, ionic gun assisted, has been adopted with what we believe are unsatifactory results.
It is our opinion that the closest prior art is that described in European Patent No. 0 502 385A dated 22.2.92 filed by Balzers, Inventor Zimmermann. In this system thin film optical interference deposition is realized by evaporation from a thermal source, with all of the limitations described above.
With this method, that is with not very thick films as in the description, the drawbacks are: insufficient hardness, insufficient durability, insufficient adherence.